The Feather M0 Bluefruit LE is a compact board which in essence is a Feather M0 Basic Proto with an on-board Bluefruit LE SPI Friend. It's small and has a Lithium Polymer (LiPo) battery charger making it ideal for this project.
Connecting an LED
The VLL protocol requires a light source to transmit the pulses to the Micro Scout. Surprisingly, the Feather's small, on-board, red LED can be used in dim ambient light. It struggles in brighter surroundings so an external LED is a better option.
The diagram above and the picture below show a brighter, white LED with a 330 ohm resistor connected between D6 and GND. In this case the resistor has been soldered to the LED and the other lead has been extended a little with the offcut from the resistor. This could be done by twisting the wires together tightly for a quick, temporary, solderless prototype. The leads are bent back at the ends to double them up to make them the fit and grip the holes removing the need for soldering to the Feather.
Care needs to be taken to ensure the wires stay clear of the other connections on the Feather board. The Blu Tack used here is holding the LED in place and also keeping the wires clear above the board. A multimeter can be used to confirm that similar putty/tak products are non-conductive.
The white LED is showing up as blue partly due to the photograph being colour-balanced for the warm ambient light.
